This paper addresses the characterization and consequences of non-ideal pressure gauge performance on pressure transient analysis. In practice, pressure measurement instruments can have response errors, including short and long term drift and anelastic relaxation, that can dramatically affect calculation of even the most basic reservoir and wellbore properties such as producibility, permeability, average reservoir pressure, and the wellbore skin factor. Best results are obtained when the pressure gauge is selected with an eye on the intended application because different types of instruments have different response characteristics.

To determine how the pressure gauge affects well test analysis, a transfer function approach is used to characterize the gauge response to changes in wellbore pressure. This model is based upon published specifications, measurement quality controls, and the fundamental physics of commonly-used transducers. This transfer function approach can also be generalized to include temperature response effects as well as the effects of noise and non-ideal gauge electronics and processing.

Specific field examples are given to illustrate how these gauge response errors affect the analysis of pressure buildup tests using the basic Homer approach as well as some of the latest computer regression techniques. Error bounds on the results of reservoir and wellbore parameter analysis are computed using a range of different gauge specifications.

The results of this approach are used to show how to optimize testing performance with cost-effective instrumentation.

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